NITRIFICATION 141 



antiseptics do upon most bacteria, inhibiting or destroy- 

 ing their growth altogether when present in very small 

 quantities. One part in 4000 of glucose or peptone will 

 retard nitrification. 



The amounts of various organic substances which were 

 found by Winogradsky and Omeliansky to retard or 

 completely check the two kinds of nitrifying bacteria are 

 given below. 



According to Boullanger and Massol the production 

 of nitrites is checked when the amount of ammonium 

 sulphate in the nutrient medium exceeds 4 or 5 per 

 cent, or when .5 per cent, or less of potassium or 

 sodium nitrite is present; more than 1.5 per cent, of 

 calcium or magnesium nitrite retards it. Almost all 

 nitrites are oxidized to nitrates so long as the 

 amount present does not exceed .05 to .1 per cent, 

 the base having little influence on the process. The 

 development and physiological activity of the nitrate 

 bacteria are diminished in the presence of more than 2 

 per cent of nitrite, and also when sodium or potassium 

 nitrate exceeds 2 or 2.5 and calcium nitrate more than 

 about 1.5 per cent. In manure heaps little nitrification 

 occurs owing to the inhibiting action of the excess of 

 organic material present and the want of good aeration. 



